Field of the Invention
The present invention relates to an attention calling system for a vehicle, which calls attention of a driver when an attention level of the driver to driving the vehicle is lowered.
Description of the Related Art
As a conventional attention calling system for a vehicle, there has been known, for example, one disclosed in Japanese Laid-Open Patent Publication (Kokai) No. H9-267660. In this system, an alertness degree of a driver is determined at predetermined time intervals, based on a steering amount obtained from operation information of a steering wheel, and the like, and alertness degrees determined by a plurality of times of determination are displayed in order on a display device at a driver's seat. Further, when there is an alertness degree determined to be not higher than a predetermined level, the color or content of a display thereof on the display device is changed or a warning sound or a voice message is output, as an alarm for calling attention of the driver.
Further, as another conventional attention calling system for a vehicle, there has been known, for example, one disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2005-62911. In this system, by analyzing an image of a driver photographed by an in-cabin camera, a state of the driver (inattentive driving or drowsy driving) is determined, and a level of danger is evaluated e.g. on a scale from 1 to 10. Then, as the level of danger is higher, a stronger alarm is performed to call attention of the driver. For example, in a case where the level of danger is low, a warning sound is output or a warning message is displayed on a monitor screen, whereas when the level of danger rises, in addition to these operations, an alarm is performed by vibrating a seat or a steering wheel.
In general, when a vehicle is traveling without any problem, a driver of the vehicle is often not very aware of a level of attention to driving or a risk of driving due to reduced attention. However, in the attention calling system disclosed in Japanese Laid-Open Patent Publication (Kokai) No. H9-267660, with indifference to such a feeling or awareness of the driver, an alertness degree of the driver is objectively determined based on operation information of the steering wheel and the like, and an alarm is performed based on a result of the determination. For this reason, the alarm is sometimes given in a state in which the driver is unaware of reduced attention and the risk of driving. In this case, since the driver cannot understand why the alarm has been given at the time, the driver has a feeling of strangeness or a feeling of distrust. Further, without a feeling of trust, the driver does not obediently follow the alarm, and hence it is impossible to effectively call the attention of the driver by the alarm.
Similarly, in the attention calling system disclosed in Japanese Laid-Open Patent Publication (Kokai) No. 2005-62911, with indifference to feeling or awareness of the driver, a state of a driver and a level of danger are objectively determined and evaluated, respectively, based on a photographed image of the driver. Therefore, it sometimes occurs that under a situation where the driver is unaware of reduced attention and the risk of driving, a high danger level is set and an alarm is issued. As a consequence, similar to the attention calling system disclosed in Japanese Laid-Open Patent Publication (Kokai) No. H9-267660, it is impossible to cause the driver to have a feeling of trust, and hence it is also impossible to effectively call the attention of the driver by the alarm. Further, in this system, an alarm to the driver is performed using tactile information having a strong stimulus by vibration of a seat or the steering wheel, and hence the feeling of strangeness or feeling of distrust of the driver becomes stronger than in the case of the attention calling system disclosed in Japanese Laid-Open Patent Publication (Kokai) No. H9-267660 in which an alarm is performed via a visual sense or an auditory sense.